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本文以滇西澜沧变质带中最为广泛分布的造岩矿物—白云母为对象，详细研究和
分析了其成分、多型类型及ba值等，探讨了白云母的发育规律。研究结果表明，本带中绝大多数白云母为多硅白云母，且为3T+2M,型，与蓝闪石共生的则以3T多硅白云母为主。此外，斓沧变质
带经历了蓝闪石片岩亚相的高压变质作用，与古特提斯构造演化密切相突，并可与世界著名的高
压带对比。 相似文献
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研究表明澜沧变质带由小黑江-西定混杂带和澜沧变质混杂带2个构造地层单元组成。前者经历了3期构造变形与2期变质作用,形成了呈南北向展布的区域性流劈理S1以及冲断-褶皱构造,主期蓝片岩相变质作用形成以蓝闪石、3T多硅白云母及黑硬绿泥石等高压相矿物为特征。后者在小黑江-西定混杂带变质变形之前业已普遍发育近东西向的褶皱构造及绿片岩相变质作用,尔后又经历了与前者相同的变形与变质历史。二者主期变质与变形作用发生在279-214Ma,与古特提斯构造发育密切相关,并形成了本带如今呈南北向展布的构造格局。 相似文献
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滇西澜沧变质带变质作用和变形作用的关系 总被引：18，自引：3，他引：18
滇西澜沧变质带经历了两期变质变形事件，其时代分别为５１９Ｍａ和２８０～１９０Ｍａ。早期变质变形事件（Ｍ１Ｄ１）可由销长石和石榴石变斑晶的包裹体痕迹确定，形成近Ｅ－Ｗ向的变形构造格局。晚期变质变形作用（Ｍ２Ｄ２）以形成蓝片岩相矿物组合，如以蓝门石（青铝门石）＋多硅白云母＋绿泥石＋石英等为特征，并形成近Ｎ－Ｓ向的变形构造格局．钠质问石以青铝闪石和蓝闪石为主，白云母多为３Ｔ＋２Ｍ；型多硅白云母，其ｂｏ均值在９．０４０Ａ以上；蓝片岩相变质作用的Ｐ、Ｔ条件估计分别为０．６～０．７ＧＰａ和３００℃。晚期变质变形事件经历了二个主要阶段（Ｍ２ａＤ２ａ和Ｍ２ｂＤ２ｂ），分别伴随透入性面理（Ｓ２）和褶劈理（Ｓ３）的形成，蓝门石的４０Ａｒ－３９Ａｒ定年分别为２７９Ｍａ和２１４Ｍａ；Ｍ２ｃＤ２ｃ期局部受到热的扰动，以及出现大量的膝折带或宽缓褶皱。上述变质变形演化历史代表了澜沧变质带的隆升及剥蚀过程。 相似文献
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位于藏北羌塘中部的冈玛日-桃形错地区首次发现含典型蓝闪石的蓝片岩。蓝片岩是由蓝闪石、铁蓝闪石、青铝闪石、多硅白云母、阳起石、黝帘石、绿帘石、方解石、榍石、金红石等矿物组成,变质温压条件为400℃±和7kbar±,属于高压变质作用。这是一条高压变质带,推测它可能向东与滇西的澜沧江高压变质带相连。冈玛日-桃形错地区含典型蓝闪石的蓝片岩的发现对羌塘陆块的重新认识以及冈瓦纳大陆与劳亚大陆的板块边界及晚古生代古特提斯洋的闭合,具有重要的大地构造意义。 相似文献
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东天山三条高压变质带地质特征和流体作用 总被引：17，自引：6，他引：17
微板块活动边缘常常产生高压变质作用,我们在东天山地区发现了三条高压变质带,分别出露在南天山北缘、中天山北缘和北天山南缘的早古生代至晚古生代地层中,它们是天山微板块多期次俯冲-碰撞-拼贴作用的产物。(南天山北缘铜花山高压变质带中有不同变异的蓝闪石类高压矿物,蓝闪石Ar~(40)/Ar~(39)同位素测定为360Ma年龄,而在同一带的西部的榆树沟有C型和B型的榴辉岩分布。中天山北缘乌斯特沟-米什沟高压变质带中发现了青铝闪石,同一阶段生成的多硅白云母为345Ma的年龄;北天山南缘后峡高压变质带中以出露在石炭世地层中钠闪石和多硅白云母为特征,三条高压变质带均经历过三个变质-变形作用阶段:①高压变质;②退变质;③韧性-脆性变质变形作用。) 流体活动与微板块构造作用密切相关,不同构造阶段有不同的变质-变形作用和矿物-流体反应:①高压变质作用阶段:微板块碰撞阶段产生不同的进变质作用,主要发生脱挥发组分的矿物反应,含水矿物转化成无水或少水矿物。南天山北缘有两次微板块与洋壳碰撞-俯冲作用,第一次碰撞-俯冲的热力学条件是:中-高温、高压和埋藏深度较大(540～720℃,0.92～1.29GPa,35～>50km),导致榴辉岩的生成,除了大量挥发组分逸出以外,另有不少熔体产生,变质矿物以捕获大量熔体和少量气-液流体包裹 相似文献
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藏北羌塘中部戈木日榴辉岩的岩石学、矿物学及变质作用pTt轨迹 总被引：5，自引：0，他引：5
羌塘中部榴辉岩位于龙木错－双湖缝合带中段,改则县古姆乡片石山地区。榴辉岩的主要矿物成分为石榴子石、绿辉石、多硅白云母、金红石、角闪石等,围岩为石榴白云母片岩和蓝片岩,石榴白云母片岩主要由石榴子石、多硅白云母和石英构成,蓝片岩由石榴子石、角闪石（含蓝闪石）、多硅白云母等构成。岩石学和矿物学研究显示,榴辉岩主要经历了3期变质作用：①峰期榴辉岩相变质作用阶段,以石榴子石、绿辉石和多硅白云母为特征,变质温度和压力分别为500℃和2.3GPa;②绿帘角闪岩相变质作用阶段,以后期形成的冻蓝闪石、镁红闪石、绿帘石、钠长石等交代早期矿物为特征;③绿片岩相变质作用阶段,以毛发状阳起石等为特征。榴辉岩的变质演化过程代表了青藏高原北部古特提斯洋俯冲消减和冈瓦纳与劳亚大陆碰撞造山的过程。 相似文献
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滇西南澜沧群多硅白云母的多型和化学成分特征及其意义 总被引：5，自引：0，他引：5
从理论、实验及实际观察的结果都表明，随着压力的增加白云母中绿鳞石的含量显著地增加，可以认为在多期变质作用过程中，尤其是在变质压力不同的多期变质作用下，形成的多硅白云母，其化学成分就会打上不同的烙印。７７个多硅白云母化学成分的统计结果表明，澜沧群低级变质岩中的多硅白云母有两种成因。在Ｎａ－Ｍｇ相关图上，反映了高压和中压变质特征，高压变质的多硅白云母约占７０％。这与用多硅白云母ｂ０值鉴别的高压和中压变质是相吻合的。多硅白云母的多型为３Ｔ和２Ｍ１型，以２Ｍ１型为主 相似文献
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The Lancang River Zone of southwestern Yunnan, China: A questionable location for the active continental margin of Paleotethys 总被引：7，自引：0，他引：7
In an attempt to constrain a Late Paleozoic tectono-metamorphic event along the Lancang River Zone, fourteen samples were processed for K/Ar dating on fine mineral fractions and detrital muscovites from this zone in southwestern Yunnan, China. The samples include mica schists, mylonites and gneisses from the Proterozoic Lancang Group and phyllites from the western part of the Simao Basin. In addition, one Ar/Ar analysis was performed on separated phengites from a blueschist of the central part of the Lancang Group. The results reveal a considerable spread of ages; the tectonic evolution of the zone is constrained by the new data, which accentuate two temporally separate, but spatially overlapping events: (i) a Late Carboniferous high-P/low-T metamorphism related to an east-vergent, Late Paleozoic thrust belt, inverting a Devonian to Carboniferous marginal basin of the Yangtze-Platform, and (ii) an upper Permian and Triassic low-P/high-T belt caused by a post-orogenic stage of rifting with distinct petrological and geochemical similarities of the igneous rocks to the Emeishan Large Igneous Province. These results imply that no active continental margin accounts for the subduction of the Paleotethys main branch, proposed to be recorded either along the Lancang River or the Changning-Menglian Belt. 相似文献
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《Journal of Asian Earth Sciences》2008,31(5-6):706-720
In an attempt to constrain a Late Paleozoic tectono-metamorphic event along the Lancang River Zone, fourteen samples were processed for K/Ar dating on fine mineral fractions and detrital muscovites from this zone in southwestern Yunnan, China. The samples include mica schists, mylonites and gneisses from the Proterozoic Lancang Group and phyllites from the western part of the Simao Basin. In addition, one Ar/Ar analysis was performed on separated phengites from a blueschist of the central part of the Lancang Group. The results reveal a considerable spread of ages; the tectonic evolution of the zone is constrained by the new data, which accentuate two temporally separate, but spatially overlapping events: (i) a Late Carboniferous high-P/low-T metamorphism related to an east-vergent, Late Paleozoic thrust belt, inverting a Devonian to Carboniferous marginal basin of the Yangtze-Platform, and (ii) an upper Permian and Triassic low-P/high-T belt caused by a post-orogenic stage of rifting with distinct petrological and geochemical similarities of the igneous rocks to the Emeishan Large Igneous Province. These results imply that no active continental margin accounts for the subduction of the Paleotethys main branch, proposed to be recorded either along the Lancang River or the Changning-Menglian Belt. 相似文献
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通过同构造沉积物质记录了解物源区剥蚀作用过程进而探索盆山构造相互关系,是大陆构造动力学研究的一个重要方面。砂岩骨架成分分析和重矿物及部分标型矿物分析方法,已被较多地用来探索新疆天山造山带与其南部库车盆地晚中生代以来的相互关系和构造演变过程,但是关于中生代较早时期库车盆地构造属性及北部造山带隆升剥蚀过程的认识仍存在较大分歧。本文运用电子探针微区成分分析方法,对库车盆地北缘中段晚三叠世和早侏罗世砂岩中具代表性的15个砂岩样品中的38颗碎屑长石和26颗碎屑白云母矿物进行了矿物化学成分分析。结果表明,长石主要来自变质岩物源区,25颗碎屑白云母均属多硅白云母,表明其源区岩石曾经历了高压变质作用。这些多硅白云母中Si原子含量显示它们比目前保留在天山造山带高压变质带蓝片岩和榴辉岩中的多硅白云母形成的压力要低,可能反映了源区高压变质岩的正常剥露顺序。这项研究结果表明,至少在晚三叠世-早侏罗世时期,库车盆地北部天山造山带中的高压变质岩已经剥露于地表并遭受剥蚀成为物源供给区。具体是中天山南缘早古生代高压变质带还是晚古生代南天山高压变质带作为重要物源区,尚需进一步的研究工作。 相似文献
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Overprinting of white micas from high pressure, low to medium temperature (M
1) metamorphic assemblages in pelitic schists on Naxos during subsequent thermal dome (M
2) metamorphism ranges from minor in the southeast of the island to complete recrystallization in the amphibolite facies rocks near the migmatites in the centre of the dome. The original (M
1) minerals are phengites (Si4+=6.7–7.0) and the overprinting minerals are muscovites (Si4+=6.0–6.45). 40Ar/39Ar step heating analyses of white mica separates from rocks in the area where phengite and muscovite occur together yield complex age spectra, characterized by low apparent ages in the first and the last stages of gas release and high apparent ages in between. These upward-convex age spectra are shown to be caused by mixing of two generations of micas, each of which has a different age spectrum and argon release pattern. Seemingly good plateaus in some age spectra from white micas of the area must be interpreted as providing meaningless intermediate ages. Further, the upward-convex age spectra have been used to trace the isotopic signature of phengites toward increasing M
2 metamorphic grade, and suggest that as long as phengites can be observed in the rocks upward-convex age spectra occur. On Naxos, crystallization of muscovite at the expense of phengite appears to be the main mechanism of resetting argon isotopic ages in white micas. However, there is also good evidence for argon loss by volume diffusion from phengites. Simple diffusion calculations suggest that the M
2 metamorphism was caused by a shortlived heat source.Now at Department of Geology, University of Alberta, Edmonton T6G 2E3, Canada 相似文献
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五台山早前寒武纪变质岩中的白云母属二八面体的2M型多型变体,其中五台群中的白云母为富含绿鳞石分子的普通白云母,滹沱群为多硅白云母。通过对这些白云母化学成分和b_0值测定,确定五台群变质条件属中低压相系,滹沱群属中高压相系。五台群绿片岩相的变质压力为0.3—0.5 GPa,滹沱群为0.5—0.6 GPa。基于白云母成分和b_0值的研究,对划分变质级别、变质类型;确定变质作用期次;进行地层对比和构造分析等方面是可行的。 相似文献